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ii                                 GLANDS   OF   THE   SKIN                               I 3
sternum, is a naked patch of skin which is seen to be perforated
by numerous pores. Besides the ordinary sebaceous and sweat
glands there are a series of masses of glands, opening by larger
orifices, which present the appearance of groups of sebaceous
glands, and are of a racemose character ; but the existence of muscu-
lar fibres in their coats seems to show that they should be referred
rather to the sudoriparous series. Beneath the integument is a
large compound tubular gland quite half an inch in diameter.
In Didelp7iys dimidiata there is a precisely similar glandular
area and large underlying gland, the correspondence being re-
markable in two Marsupials so distant in geographical position
and affinities. Even among the Diprotodont genera there is
something of the kind; for in Dorcopsis luctuosa and D. wiuelleri
is a collection of four unusually large sebaceous follicles upon
the throat, and in the Tree Kangaroo (JDendrola-gus bennettii')
there is the same collection of enlarged hair-follicles, though
they are apparently somewhat reduced as compared with those of
Dorcopsis. These are of course a few examples out of many.
It seems to be possible that the functions of these various
glands is at least twofold. In the first place, they may serve,
where predominant in one sex, to attract the sexes together.
In the second place, the glands may be useful to enable a strayed
animal of a gregarious species to regain the herd. It is perfectly
conceivable too that in other cases the glands may be a protec-
tion, as they most undoubtedly are in the Skunk, from attacks.
In connexion with the first, and more especially the second, of
the possible uses of these glands, it is interesting to note that
in purely terrestrial creatures, such as the Rhinoceros, the glands
are situated on the feet, and would therefore taint the grass and
herbage as the animal passed, and thus leave a track for the
benefit of its mate. The same may be said of the rudimentary
glands of Horses if they are really glands. The secretion of the
" crumen." of Antelopes is sometimes deposited deliberately by
Oreotragus upon surrounding objects, a proceeding which would
attain the same end. One may even perhaps detect " mimicry "
in the similar odours of certain animals. Prey may be lured to
their destruction, or enemies frightened away. The defenceless
Musk-deer may escape its foes by the suggestion of the musky
odour of a crocodile. It is at any rate perfectly conceivable
that the variety of odours among mammals may play a very